1. Field of Invention
This invention relates to fuel sources for electrochemical cells such as hydrogen fuel cells.
2. Background
Hydrogen fuel cells have been proposed utilizing a reactive chemical hydride as a fuel source. Normally the chemical hydride is reacted with water to liberate hydrogen gas, which then is consumed by the fuel cell. Other protonic solvents besides water (e.g. alcohols, organic acids) may also be employed.
In such a fuel cell system, a housing is often employed to contain the fuel and reaction products in order to protect the fuel from reacting with atmospheric moisture when the fuel cell is not in service and to collect the generated hydrogen so it can be conducted to the fuel cell. It is desirable to include a maximum quantity of fuel in a housing of a given volume in order to achieve the highest possible hydrogen output and the longest possible running time for the fuel cell. However, the disadvantage of packing fuel too tightly into the housing is that the access of water to some parts of the fuel becomes restricted and the rate of hydrogen generation is then limited by the slow diffusion of water into the bulk of the fuel. As solid reaction products accumulate, they may further restrict water access, choking off the reaction. Ultimately, the reaction may reach a standstill and fuel utilization will be incomplete.